Leatherback turtles can grow up to 6 feet long and hold the distinction of being the largest turtles and the largest living reptiles in the world. But they are also among the most critically endangered of species, according to the IUCN Red List of Threatened Species.
Now, at least, conservationists can zero in on where to help these reptiles. A new study of leatherback turtle migration patterns has identified Pacific Ocean danger zones for these turtles. The danger zones are high-use areas, so identifying them can help inform decisions about fishing practices that are harming these majestic animals.
"The study (accepted for publication in the April issue of the journal Ecological Applications) shows that leatherbacks can be found throughout the Pacific Ocean and identifies high-use areas that are of particular importance to their survival," lead author Helen Bailey of the University of Maryland Center for Environmental Science said in a press release.
"This information on their movements is essential for identifying hot spots and assessing where limiting fishing at particular times of year may be effective for protecting leatherbacks."
Female leatherbacks lay clutches of about 100 eggs on sandy, tropical beaches. After the babies hatch, they must struggle to get off the beach and into the water. As this video shows, even a small pile of sand can become a major obstacle, and few of the youngsters survive while out at sea.
The study focused more on adult leatherbacks, however. They migrate to foraging areas to feed on jellyfish. These long-distance migrations increase the risk that these animals become caught in fishing gear, undermining conservation efforts to protect turtles on their nesting beaches.
Interaction with fisheries is believed to be a major cause of death, which is of particular concern in the eastern Pacific Ocean, where the number of leatherback turtles has dropped by more than 90 percent since 1980.
"Leatherback turtles are long-lived animals that take a long time to reach maturity, so when they are killed in fishing gear it has a huge impact on the population," said study coordinator James Spotila of Drexel University. "Their numbers are declining so rapidly it is critical that measures are taken quickly to ensure these animals don’t go extinct."
For the study, the researchers used satellite tracking devices to follow the movements of 135 turtles as they swam from Costa Rica, Mexico, Indonesia and off the coast of California.
The study found that the western Pacific population nesting in Indonesia traveled to many different feeding sites in the South China Sea, Indonesian seas, southeastern Australia and the U.S. West Coast, mainly in highly productive coastal areas. This wide dispersal allows for a greater likelihood of finding food. It also means that the turtles are more vulnerable to being caught in fishing gear.
The eastern Pacific population had a very different migration pattern, traveling from their nesting sites in Mexico and Costa Rica to the southeast Pacific. These turtles migrated south and tended to feed in offshore upwelling areas where their food, almost exclusively jellyfish, may be concentrated.
The more limited feeding grounds of the east Pacific turtles make them more vulnerable to any changes in the distribution or abundance of jellyfish in this area.
Human-related deaths, such as being caught in fishing gear, also pose a greater risk of causing this population to go extinct because they have a smaller range than the western Pacific leatherbacks.
At least now scientists have a better idea of where these large turtles nest and migrate. The identified hot spots will hopefully lead to altered fishing practices and conservation efforts in those key areas to give the turtles a fighting chance.